Adelobasileus
Adelobasileus cromptoni is a genus of mammaliamorph cynodonts from the Late Triassic, about 225 - 220 million years ago. It is known only from a partial skull recovered from the Tecovas Formation in western Texas and partial specimens from the Chinle Formation in Arizona, Southern [United States].
Distinct cranial features, especially the housing of the cochlea, suggest that Adelobasileus is a transitional form in the character transformation from non-mammaliaform cynodonts to mammaliaforms. For this reason, it is thought to be a close relative of the common ancestor of all modern mammals. Though formerly classified as a mammal by trait-based taxonomy, it is currently placed outside the crown group containing all true mammals.